Trump followed that up a few hours later with a lengthier statement, in which he called Castro a "brutal dictator who oppressed his own people for nearly six decades" and said he hoped Castro's death gave Cuban Americans "the hope of one day soon seeing a free Cuba."

"Fidel Castro's legacy is one of firing squads, theft, unimaginable suffering, poverty and the denial of fundamental human rights," the statement said.

"While Cuba remains a totalitarian island, it is my hope that today marks a move away from the horrors endured for too long, and toward a future in which the wonderful Cuban people finally live in the freedom they so richly deserve."

Trump added: "Though the tragedies, deaths and pain caused by Fidel Castro cannot be erased, our administration will do all it can to ensure the Cuban people can finally begin their journey toward prosperity and liberty."

Trump has been sounding off against Castro for decades — and battled criticism for reportedly exploring whether to open a casino in Cuba in the 1990s.

Trump came under intense scrutiny in September following allegations that he knowingly violated the U.S. embargo on Cuba in the 1990s, news that threatened to sour Cuban Americans' opinion of him.

A Newsweek story said that Trump spent $68,000 to send business consultants to Cuba despite the embargo. Trump Hotels reimbursed Seven Arrows Investment & Development Corp., an American consulting firm, shortly after Trump launched his bid for the White House, according to the article.

In the op-ed, Trump wrote that "it would be instructive to remember the role that Castro played in the struggle between — yes — good and evil."

"He turned his island over to his Soviet patrons," Trump continued. "He was quite willing to have nuclear missiles, launched from Cuban soil, destroy American cities. He exported revolution to Central and South America. He abetted Libyan terrorism. He gave asylum to murderers. He posted troops in Africa.

"More important, he turned his nation into a maximum-security prison. His regime controls every aspect of human life - access to food, medical assistance, schools and employment. Castro has not mellowed with age. Terror continues to reign. The secret police are unrestrained. The disappearance and beatings of citizens are still tools of civilian control, as is the suppression of free speech. Castro's ruthless domination of the Cuban people has not lessened even as his regime crumbles."

In his book, "The America We Deserve," Trump said Castro should be arrested and tried.

“The first time Castro leaves Cuba for any nation we have extradition treaties with, he should be detained, arrested and extradited to the U.S. for indictment and trial on charges of murder and terrorism,” according to an excerpt in Townhall.com.

As Trump ran for President, he said he was in favor of President Obama's efforts to normalize relations with Cuba, although he blasted Obama for a “one-sided deal for Cuba,” according to The Washington Post's Jose A. DelReal.

Trump had vowed to reverse Obama’s efforts to open U.S. relations with Cuba if he was elected president, “unless the Castro regime meets our demands — not my demands, our demands.”